Find the value
\[ x + \sqrt{15} = 4 \]
Solution:
\[ x = 4 – \sqrt{15} \]
\[ \frac{1}{x} = \frac{1}{4 – \sqrt{15}} \times \frac{4 + \sqrt{15}}{4 + \sqrt{15}} \]
\[ = \frac{4 + \sqrt{15}}{16 – 15} = 4 + \sqrt{15} \]
\[ x + \frac{1}{x} = (4 – \sqrt{15}) + (4 + \sqrt{15}) \]
\[ = 8 \]
\[ \therefore \text{Correct Answer: } 8 \ (\text{Option c}) \]